Understanding Bugs So What Defines an Insect?
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AL A B A M A A & M A N D A U B U R N U NIVERSITIES ANR-1289 What’s Buggin’ You? ll animals, including insects, exist only in suit- able habitats with places to shelter, eat, and So what defines an insect? reproduce. In a location that lacks one or more of these requirements, they fail to thrive All insects have the following: or even survive. • A hard, protective exoskeleton they must A molt (shed) to grow larger Location is also important for a healthy garden whether planting ornamental, vegetable, flower, or even turf • Multiple life stages (e.g., egg, larvae, areas. Healthy plants have fewer pest problems than nymph, pupae, and adult) those stressed plants in unfavorable locations. Each plant has its own specific needs for sunlight, water, • A body with bilateral symmetry fertility, soil type, and temperature. When gardeners • Three body parts: put plants in unsuitable areas, pest problems, such as insects, often appear. - Head – with compound eyes, a mouth, and antennae Most insects, however, are not pests. The following is a guide to help distinguish some of the more common - Thorax – the wings (if present) and garden and household insects, their groups, and their legs are attached here purpose. Learn their role and discover what part of - Abdomen – it is often the largest their cycle can potentially affect you and your garden. body part where the primary life Gain an understanding of true pests, minor nuisances, functions occur benign residents, and beneficial “bugs.” • Three pairs of jointed legs Understanding Bugs Did you know that of the 1.5 million identified animals Metamorphosis on this planet, more than half are insects? And, most Observing insect development helps us identify them, insects are beneficial to humans. For example, the rav- understand their purpose, and also understand the best enous lady beetle, or ladybug, can eat as many as 2,400 time to apply specific control measures if necessary. aphids in its lifespan. Metamorphosis means a change in form, structure, or function as a result of development. This change How do you determine if your garden is hosting pest requires molting the hard, protective exoskeleton and insects or beneficial insects? This can be difficult can be generally described as either incomplete because circumstances often determine the insect’s or complete. role. Honeybees can be both. If provoked, they deliver nasty, painful stings. However, bees also assist in pol- Insects having incomplete metamorphosis gradually linating many fruits and vegetables. Some insects eat change through three stages: egg, nymph, and adult. other plant-damaging insects. Many insects are food for Hatching from an egg, the immature often looks like a ARCHIVEsmaller, wingless version of the adult, called a nymph. various animals and some are beneficial decomposers, and the small number of species that harm plants and The adult stage results after numerous nymphal molts. animals are known as pests. Adults are the reproductive and final developmental stage. Stink bugs, cockroaches, aphids, and grasshoppers are examples of insects having incomplete metamorphosis. www.aces.edu Insects with complete metamorphosis have four stages: Life cycle information helps determine what and when egg, larva, pupa, and adult. The larvae hatching from control options are most likely effective. In general, eggs look quite different from the adults, often use a there is at least one stage in the insect’s cycle when it is different food source, and many times have different most vulnerable to the selected control methods. Timing types of mouthparts. For example, the larval stage of of controls is just as important as choice of control. a butterfly or moth has chewing mouthparts while the adult butterfly or moth has siphoning mouthparts. These Insect Groups larvae later become nonfeeding, stationary pupae inside It is also helpful to learn some common characteristics a protective case. The larva inside each pupal case of the insect groups (scientific orders). This can help liquefies and reforms into an adult. Examples are distinguish the good from the bad, or at least give you moths and butterflies, flies, ants, and beetles. some understanding of their purpose. Scientific Order (name) Common Name Description Activity or Role Araneae and Acarina spiders, mites, and not true insects, but still spiders eat insects and other chiggers distant relatives; eight small animals; many mites are legs; two body parts – plant and animal pests; some cephalothorax and mites are beneficial predators abdomen; no antenna of insects and other mites Coleoptera beetles hard wings cover the some are helpful to plants, soft flight wings below some are damaging to plants Dictyoptera cockroaches and cockroaches are decom- front wings are completely leathery; praying mantids posers, eating any dead hind wings are membranous; some materials; mantids prey fly, some don’t on other insects Diptera flies and mosquitoes one pair of flight wings some of the most notorious animal disease vectors (e.g., mosquitoes and tse-tse flies); some flies lay eggs in garden fruits, making the fruit unsightly or inedible; a few fly larvae are leaf and stem eaters Hemiptera true bugs (leafhoppers, forewings are half some are helpful, some are stink bugs, lace bugs, hardened, or leathery, damaging to plants; a few are pirate bugs, and and half membranous human pests (e.g., bed bugs) assassin bugs) Homoptera cicadas, leafhoppers, uniform wings; all eat plant sap; some feed on only aphids, scale insects, wedge-shaped head one type of plant; sometimes only whiteflies, and others the nymphs cause damage Hymenoptera ants, wasps, and bees two pair of membranous many are beneficial in the garden wings; thin “waist” between and nonstinging; some humans abdomen and thorax; many are highly allergic to those with are colonial a venomous sting Isoptera termites both wing pairs are see ANR-1170, ANR-1035, ARCHIVEidentical and equal in size ANR-1252, ANR-1022 Lepideptera butterflies and moths wings covered by scales, nectar feeding adults pollinate sometimes with colorful flowers; the larvae, or caterpillars, patterns eat plant leaves and stems Odonata dragonflies and toothed mouthparts; all are predators on other damselflies distinctive wing patches insects and, when nymphs, for each species other aquatic creatures 2 Alabama Cooperative Extension System Scientific Order (name) Common Name Description Activity or Role Orthoptera grasshoppers, katydids, straight, nonfolding wings; all grasshoppers are plant eaters – mole crickets, and long hindlegs for jumping some more damaging than others; crickets crickets are decomposers, eating any dead materials; mole crickets eat only plant roots; katydids are also plant eaters Siphonaptera fleas siphoning mouthparts; pests of mammals wingless, flattened body Common Garden Sightings both larvae and adults have chew- ing mouthparts. Some feed on Araneae and Acarina – spiders and mites plants, some just on plant pollen. Spiders are not insects, but they are a specialized group Some beetles feed on other insects, of animals often producing silken webs for catching prey. some on fungi, and others are Spiders without webs ambush prey. Some use under- decomposers, eating dead plants ground burrows to hide while others change color for and animals. camouflage. In any case, spiders are often considered Some of the more commonly beneficial to the garden because their primary food is known plant pest beetles are the insects. Spiders have incomplete metamorphosis and a elm leaf, Japanese, June, cucum- solitary lifestyle. In the United States, only the brown ber, potato, and Mexican bean beetles. Pest beetles can recluse, and black and brown widow spiders are be trunk and stem borers, leaf miners, root feeders, leaf dangerous to people. eaters, or whole plant eaters. Some predatory, beneficial Mites are also non-insects, and beetles are lady, soldier, tiger, and ground beetles. The some are serious pests causing leaf first key to control is identification. Preserve the benefi- galls, plant death, or irritation to cial beetles that snack on slugs, aphids, caterpillars, and animals. They all have needle-like other pests. mouthparts to puncture tissue and suck out liquids. Those that bite humans, such as chiggers and ticks, Dictyoptera–mantids and cockroaches are irritating, and some ticks spread Praying mantids are one of the larger garden insects; disease. Avoid wild areas with dense some can be up to 4 inches long. They hide in the vegetation, especially tall grasses, garden by camouflage and have heightened vision and to prevent bites. Insect repellents and long pants tucked hearing for sensing insect prey. Their front into socks are recommended if you visit suspect areas. legs are spined to assist with catching prey. When a few mites feed on leaves and flowers, affected They are the only insects able to rotate tissues appear speckled (stippled) while webbing and their heads. Mantids have incomplete dead tissue appear with larger mite populations. Preven- metamorphosis, laying 100 or more eggs in tion is relatively easy if you know spider mites thrive a spongy mass. during hot, dry weather. A good spray of water disrupts Labeling mantids as beneficial or pest reproduction and feeding. Spray the underside of leaves insects is difficult. They do eat insects that where they hide and repeat daily if plants are infested. harm your plants, but are just as willing Frequent monitoring during dry summer days is a must. to snack on a butterfly or lady beetle. All Mites also tend to attack plants under stress, so keeping insects, even other mantids, are equally plants healthy is the firstARCHIVE line of defense. treated as just another meal. Mantids must be solitary for survival. You are most likely to see man- Coleoptera–beetles tids in late summer or fall when adults are full-sized. Beetles comprise the largest and most diverse of all While cockroaches are certainly household pests, they insect groups. In fact, they comprise 25 percent of all also serve an important purpose: eating decaying organic animals on Earth.